The present invention relates to the deposition of a high quality coating containing silicon and oxygen from vaporized hydrogen silsesquioxane resin wherein the formed coating has minimal impurity from incomplete oxidation. The process comprises introducing the hydrogen silsesquioxane vapor into a deposition chamber containing the substrate to be coated and containing a reactive environment comprising nitrous oxide, and then inducing reaction of the vapor to form the coating.
Silica vapor deposition methods in a reactive environment comprising nitrous oxide (N.sub.2 O) are known in the art and many are currently used in industry. Typically, such deposition methods involve decomposing a monomeric silicon source (e.g., SiH.sub.4, SiH.sub.2 Cl.sub.2. etc.) in the presence of nitrous oxide to form a silicon dioxide dielectric coating.
Kemlage in U.S. Pat. No. 4,239,811 teaches a low pressure vapor deposition method which deposits silicon dioxide coating by reacting monomeric chlorosilanes with nitrous oxide in the presence of oxygen. Kemlage found that the oxygen input produces silicon dioxide layers which are more resistent to degradation during subsequent oxidation cycles. This patent, however, only describes the use of monomeric silane compounds with nitrous oxide.
The use of hydrogen silsesquioxane resins in solution to form coatings is likewise known in the art. For instance, Haluska et al. in U.S. Pat. No. 4,756,977 teach the use of hydrogen silsesquioxane to form ceramic coatings on substrates. Similarly. Haluska et al. in U.S. Pat. No. 4,808,653 teach the use of hydrogen silsesquioxane in combination with other metal oxide precursors to form ceramic coatings on substrates. These patents, however, only describe the use of the resin in solution.
Gentle, U.S. Pat. application No. 07/706,464, filed 5/28/91, now allowed, describes the use of vaporized low molecular weight hydrogen silsesquioxane for the deposition of a silicon and oxygen containing coating on a substrate. The reactive environment claimed therein included ammonia, air, oxygen, and amines. The reference, however, did not teach that low molecular weight hydrogen silsesquioxane can be used with nitrous oxide in the process claimed herein.
Ballance et al. in U.S. Pat. application No. 07/912,436 filed 7-13-92 and assigned to the same assignee hereof, describe curing hydrogen silsesquioxane resin with nitrous oxide. This application, however, is limited to curing the resinous polymer as compared to the vaporized species claimed herein.
The present inventors have now unexpectedly discovered that the reaction of nitrous oxide with gaseous, low molecular weight hydrogen silsesquioxane in conventional vapor deposition techniques can form high purity silicon and oxygen containing coatings.